The present invention relates to control systems for current-sensitive control devices, and more particularly, to more accurate control of current-sensitive control devices through resistance measurement techniques.
Prior attempts to control a common device with the greater of the outputs from two controllers have required that the control device be fitted with dual control coils as described in U.S. Pat. No. 4,043,607 to Signorelli et al. or that additional hardware be added as described in U.S. Pat. No. 4,412,291 to Amberg et al. to select the greater of the two output signals to be applied to the control device. Diode selection circuits have been utilized heretofore as exemplified by U.S. Pat. No. 3,461,315.
It is accordingly an object of the present invention to provide accurate control of a current-sensitive device e.g. a servovalve which is controlled by two parallel connected controllers, one being a current driver controller and the other a voltage driver controller. Control voltages from the voltage controller are applied subsequent to resistance measurement of the servovalve coil.
In accordance with a preferred embodiment of the present invention, the method of resistance measurement on the servovalve coil is accomplished through a series of sequential steps and computations utilizing the voltage driver controller.
Further objects and advantages of the invention will become apparent from the following description, which is given by way of example, with reference to the accompanying drawing, in which: